nav2_ros_common interfaces for Services, Subscription, and Action to be lifecycle enabled

[SteveMacenski]

Following in the footsteps of the lifecycle publisher, enable the subscription, action server, action client, service server, and service client to have an activate and deactivate method for lifecycle enablement.

These should be added as managed entities and update the Nav2 Task Servers to call a new method nav2::LifecycleNode::activateInterfaces() and complimentary in deactivation so that these are all automatically activated and deactivated behind the scenes. Update the task servers to remove the manual activation and deactivation. We do need to take some care that the instantiation of the interfaces then are ordered since some subscription callbacks might depend on some publishers activation or existence. So we should be creating all exporters (i.e. action clients, service clients, publishers) before consumers (i.e. actions, services, subscribers) -- and deactivating all consumers before exporters (inverted).

On top, in the nav2 lifecycle node, we should autoactivate if the node is already activated when an interface is created (see nav2::Publisher for example)

[SuperGops7]

Hey @SteveMacenski I'd like to work on this

[SteveMacenski]

Awesome! I think it makes sense to start off small and do this bit by bit. How about you come up with a game plan and we have some incremental PRs to do this one at a time (subscribers, actions, services, clients, action clients)! Somewhere in there (perhaps after the first?) we should incorporate the boilerplate I mentioned with activateInterfaces so that later changes aren't as involved

[kailash197]

Hi @SteveMacenski I would like to contribute in this issue. @SuperGops7 any update so far?

[SteveMacenski]

I don't believe so - please feel free to get involved!

[ar-py-grim]

Hi, i would love to contribute to this issue

[SteveMacenski]

Please do! It might be good to start by breaking down the elements and tackling them one at a time so we have smaller bite-sized PRs we can review and merge in case there's any problems (and makes it much easier for me to review)

[ar-py-grim]

Is somebody also working on it, would love to join them

[SteveMacenski]

Perhaps @kailash197 - can you chime in?

[kailash197]

@ar-py-grim I am still studying the codes, can't figure out where/how to start. This is first issue that am working on.
@SteveMacenski any suggestions on where to start?

[ar-py-grim]

Ohk, maybe we can do this together. @SteveMacenski pls give us some suggestions how to approach this issue

[SteveMacenski]

Step 1

I think we should start with the subscription first since its the most straight forward. We want to update the subscription in nav2_ros_common to have the lifecycle transitions implemented, which you can look at the rclcpp_lifecycle Publisher for reference [1] which uses the ManagedEntity class to handle the transitions and states [2].

Once we have those transitions, we can use them to check is_activated() before processing callbacks to the client callback it stores. If not, log that the subscriber is not enabled yet (similar to [1]).

[1] https://github.com/ros2/rclcpp/blob/rolling/rclcpp_lifecycle/include/rclcpp_lifecycle/lifecycle_publisher.hpp#L38
[2] https://github.com/ros2/rclcpp/blob/rolling/rclcpp_lifecycle/include/rclcpp_lifecycle/managed_entity.hpp

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Step 2

That process then should repeat with the Services, Clients, and Action Servers.

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Step 3

Once we have all of them being lifecycle-enabled, we can then update the Nav2 Lifecycle Node implementation to use a nav2::LifecycleNode::activateInterfaces() whereas we create all publishers, then clients, then action clients, then subscriptions, services, and action servers, respectively. That way all 'processing' tasks are activated only once all 'information' tasks are provided. At that point, we can remove all of the activate() / on_activate() calls from the Nav2 lifecycle node transition functions which would make that code much more concise and handled behind the scenes.

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Step 4

Finally, On top, in the nav2 lifecycle node, we should autoactivate if the node is already activated when an interface is created (see nav2::Publisher for example)